Hi,

as others already pointed out, there are more factors to be considered.

As for Raid5 vs. raid1+0,
the later will almost surely improve overall performance at higher costs.

Changing to either raid 1 or raid1+0 will likely 
etremly speed-up tasks where the database is changed,
like client backups or the restoration of DB itself.

As for database I would consider 2 raid1 arrays over single rad1+0 array,
and a separate dbvolume per each raid1 array.

This could considerably speed your database reads and writes.
Allowing for 2 separate dbvolumes per each raid1 array
would even further sped the reads - 
as there were up to 4 paralell I/0s - one per spindle.
But writing would cause up to 8 parallel I/Os - 2 per spindle,
which could slow things down.

But - if your disk controller has a fair amount of cahce
this would not matter much,
and you could define even more dbvolumes.
With my controller with 128MB ram and nice
access optimisation
4 dbvolumes per raid1 are better than 2,
but - it depends.

Raid1+0 would be nice for backup storage pools,
if you can afford it.


....
Regards
Juraj Salak